Olszyk, David M. and C.W. Wise. 1997. Interactive effects of elevated CO2 and O3 on rice and flacca tomato. Agriculture, Ecosystems, and Environment 66:1-10.
Atmospheric concentrations of both carbon dioxide (CO2) and ozone (O3) are increasing, with potentially dramatic effects on plants. This study was conducted to determine interactive effects of CO2 and O3 on rice (Oryza sativa L. cv. IR 74) and a "wilty" mutant of tomato (Lycopersicon esculentum Mill. flacca). Plants were grown from seed in a glasshouse and exposed for 28 days to ambient or elevated CO2 (400 or 700 L L-1 CO2) and/or ambient or elevated O3 (peak/valley pattern of exposure with cumulative totals of 1 or 44 L L-1-hr). Elevated CO2 alleviated O3 associated decreases in allocation of biomass to roots, as indicated by a decreased root/shoot ratio (p<0.05), and also reduced injury from O3 as indicated by leaf greenness readings for one experiment (p<0.05). By itself, elevated CO2 resulted in increases in total plant and individual organ (root, leaf, stem) dry weights and root/shoot ratio; and elevated O3 resulted in increases in main culm leaf number and a decrease in stem dry weight (p<0.05). Elevated CO2 had no significant effect on the tendency for O3-induced biomass reductions of flacca tomato. For flacca, elevated CO2 alone increased shoot and root biomass (p<0.05), and elevated O3 alone tended to decrease biomass for both parameters, but only at p=0.09 and 0.11, respectively. This study was preliminary as the environmental conditions in these experiments may have altered O3 and CO2 responses of the plants. However, these results provided additional evidence that elevated CO2 inhibits adverse effects of O3 on plants, and that the interactive response may be mediated by stomata.